Cool weather blamed: Weeds abundant in Arkansas fields

Lamar James | May 20, 2005

Rain and unseasonably cool weather recently conspired to challenge the production skills of Arkansas farmers. The cold weather and rain mix have stressed newly planted crops.

The cold temperatures also caused herbicides to lose some effectiveness, according to Bob Scott, Arkansas Extension weed specialist. “We've got a lot of farmers who have put out their Command or other soil-applied herbicides. But a lot of weeds have broken through, causing problems.”

During the recent cold snap, propanil, an important herbicide, lost effectiveness.

“We're having a lot of grass problems. Grass weeds are the number one weed problem in rice. It can cost you a crop. Fortunately, much of it is still small.”

Scott said the recent warming trend is a good time to apply herbicides. In addition to grass, smartweeds and other broadleaf weeds have popped up in fields.

Scott said there are many herbicides farmers can use as it warms up. Many propanil products can control smaller smartweeds. Aim and Storm can also be used.

“When a smartweed reaches 5 or 6 inches it becomes difficult to control. A lot of products, such as Aim and Storm, will burn it back or burn leaves but re-growth will occur four to six weeks, and farmers often have to treat again. Once it reaches that size we change our mix to include other herbicides such as Regiment, Permit or Duet.”

This combination, he said, is more effective on bigger smartweeds. “There have been no drift problems with Command this year that I'm aware of,” Scott noted. “Ken Smith (another Arkansas Extension weed specialist) says that reports of Roundup drift damage to corn problems, so far, are down this year. We're not out of the woods yet. Rice is emerging, and farmers need to be aware of drift problems through harvest.”

Smith said there are two reasons for the drop in drift reports. “One is that we just haven't had the constant high winds like we did last year. Two, we've got more people who planted more Roundup Ready corn as a preventive. After planting last year, the wind blew, and it rained. Some farmers applied herbicides when they didn't need to.”

Smith said he's seeing more cold weather problems now. He said some farmers have complained they must be having a drift problem because their cotton, corn and soybean crops are sick.

“But when you go look at the crops, most of it is cold weather damage. We've seen a lot of corn injured. We normally don't see much cold weather injury to corn. Some cold weather symptoms are similar to herbicide drift symptoms. We're just not accustomed to some of the recent record-breaking cold temperatures.”

Smith said it's supposed to warm up soon. When that happens, he expects crops to respond quickly and grow out of their stress with no problem.

“I'd like to see farmers hold off on herbicide applications to give crops time to recover from the cold, if they're seeing sickly looking crops in their fields. You don't want to put additional stress on the crops. Weeds aren't growing fast because of the cold, so farmers have a little breathing room.”

Weeds will be easier to kill when it warms up and they begin growing again normally. “But, if crops are healthy and weeds are growing, you'd better go ahead and spray them.”

Lamar James is an Extension communications specialist with the University of Arkansas.